Motoneuron development and spinal cord patterning

Dr. Lance-Jones' research focuses on the development of motoneurons and their axonal projections in the vertebrate embryo. During early embryogenesis, motoneurons acquire unique molecular profiles as a result of their position with respect to specific signaling centers. Subsequently, these molecular profiles are translated into stereotyped patterns of motor columns or nuclei and specific patterns of connectivity with both somatic and visceral targets. Trainees in Dr. Lance-Jones' laboratory are currently studying aspects of these processes in three different groups of developing motoneurons. The muscles of the hindlimb are innervated by motoneurons located within the lateral motor columns of the lumbosacral cord. Members of Dr. Lance-Jones' lab are addressing the roles of Hox transcription factors in the early diversification of lumbosacral motoneuron progenitors using both in ovo electroporation in the chick embryo as well as assessments of motoneuron organization in Hox loss-of-function mice embryos. Little is known about the origins of a second group of motoneurons in lumbosacral regions, the postganglionic motoneurons that innervate caudal or pelvic viscera and arise from the caudal neural crest. Avian chimera production and cell tracing experiments are being employed to identify the specific origins of pelvic ganglia and to characterize spatial and temporal features of molecular differentiation. Finally, studies carried out by Dr. Lance-Jones' research group are addressing questions about the identity and distribution of axon guidance cues influencing target choice among motoneuron populations that innervate extraocular muscles.

How and when do motoneurons acquire a target identity? How is the early limb bud populated by muscle cell precursors? How does the early spinal cord acquire differences along its cranio-caudal axis? Trainees in Dr. Lance-Jones' laboratory have the opportunity to study embryonic patterning at tissue, cell and molecular levels. In vivo embryonic surgery is frequently combined with new techniques for identifying different types of embryonic cells. Such techniques might include long-lasting fluorescent cell markers, monoclonal antibodies, retroviral vectors, and/or gene probes. Currently, laboratory members are specifically looking at the roles of hox genes and paraxial mesoderm in the early regional development of the spinal cord.